Partially binding to a list - wpf

Question

I have a collection of a few thousand elements and I want to display only a subset of them. Is there a way to bind the collection to a view such that only certain elements, e.g. those with property "Show == true", are displayed? If so, would it still create thousands of UI elements? Or do I have to create a new list of the to-be-shown elements?

Answer 1

Check CollectionViewSource Class and CollectionViewSource.Filter Event
View(partial example):
<Grid>
<Grid.DataContext>
<wpfCalc:StudentList/>
</Grid.DataContext>
<Grid.Resources>
<CollectionViewSource
Source="{Binding Students,Mode=OneWay}" x:Key="StudentsCollViewSource"
Filter="StudentsCollViewSource_OnFilter"/>
</Grid.Resources>
<ListBox ItemsSource="{Binding Source={StaticResource StudentsCollViewSource}}">
<ListBox.ItemTemplate>
<DataTemplate>
<TextBlock Text="{Binding Name,Mode=OneTime}"/>
</DataTemplate>
</ListBox.ItemTemplate>
</ListBox>
</Grid>
And code behind filter implementation:
private void StudentsCollViewSource_OnFilter(object sender, FilterEventArgs e)
{
var s = e.Item as Student;
e.Accepted = s != null && !string.IsNullOrWhiteSpace(s.Name);
}

Answer 2

There are two methods. First one is to use a converter.
<Window.Resources>
<local:BoolToVisibilityConverter x:Key="converter"/>
</Window.Resources>
<StackPanel>
<ListView x:Name="listView" ItemsSource="{Binding List}">
<ListView.ItemTemplate>
<DataTemplate >
<TextBlock Text="{Binding Name}" Visibility="{Binding IsActive, Converter={StaticResource converter}}"/>
</DataTemplate>
</ListView.ItemTemplate>
</ListView>
</StackPanel>
//Code Behind
public class BoolToVisibilityConverter : IValueConverter
{
#region IValueConverter Members
public object Convert(object value, System.Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return (bool)value ? Visibility.Visible : Visibility.Collapsed;
}
public object ConvertBack(object value, System.Type targetType, object parameter, System.Globalization.CultureInfo culture)
{
return false; // not needed
}
#endregion
}
Second method is to use linq
List<MyData> list
{
get
{
if(list!=null)
return list.where( p => p.IsActive == true );
return null;
}
set
{
if(list!=value)
list = value;
}
}